JEE Main 2024 — Redox Reactions Question with Solution

In disproportionation reaction,  both oxidation and reduction of same chemical species occurs.

• Oxidation is gain in oxidation number.
• Reduction is loss in oxidation number.

$1)$ ${\mathrm{Cu}}^{+}⟶{\mathrm{Cu}}^{2+}+\mathrm{Cu}$

Oxidation state of ${\mathrm{Cu}}^{+}=+1$.

Oxidation state of ${\mathrm{Cu}}^{2+}=+2$.

Oxidation state of $\mathrm{Cu}=0$ .

Here, ${\mathrm{Cu}}^{+}$ is getting both reduced and oxidised.

$2)$$3{\mathrm{MnO}}_4^{-}+4{\mathrm{H}}^{+}⟶2{\mathrm{MnO}}_4^{-}+{\mathrm{MnO}}_2+2{\mathrm{H}}_2\mathrm{O}$

Oxidation state of $\mathrm{Mn}$ in ${{\mathrm{MnO}}_4}^{-}=+7$.

Oxidation state of $\mathrm{Mn}$ in ${\mathrm{MnO}}_{2 }=+4$.

Here, reduction is taking place.

$3)$$2{\mathrm{KMnO}}_4⟶{\mathrm{K}}_2{\mathrm{MnO}}_4+{\mathrm{MnO}}_2+{\mathrm{O}}_2$

Here in the reaction, $\mathrm{Mn}$ is changing its oxidation state from $+7$ to $+6$and $+4$. In both cases, reduction is occurring.

$4)$$2{\mathrm{MnO}}_4^{-}+3{\mathrm{Mn}}^{2+}+2{\mathrm{H}}_2\mathrm{O}⟶5{\mathrm{MnO}}_2+4{\mathrm{H}}^{+}$

Here in the reaction, product with $\mathrm{Mn}$ in only one, so there is no possibility of both oxidation and reduction reactions at the same time.